Side-coupled Cladding-pumped Fiber Research Articles

20 kW Laser Output Based on Homemade (1+1) Distributed Side-Coupled Cladding-Pumped Fiber

20 kW Laser Output Based on Homemade (1+1) Distributed Side-Coupled Cladding-Pumped Fiber

Temperature characteristic of a gain fiber core in distributed side-coupled cladding-pumped fiber amplifiers with different pump schemes

In this paper, we study the temperature characteristic of a gain fiber core in distributed side-coupled cladding-pumped (DSCCP) fiber amplifiers by optical frequency domain reflectometry (OFDR). To the best of our knowledge, this is the first temperature distribution measurement of a fiber core in DSCCP fiber lasers. The temperature distributions are also firstly measured among forward, backward, and bidirectional pump schemes. In addition, the bidirectional pump scheme has lower temperature distribution than unidirectional pump schemes. The experimental fiber core temperature is in according with the numerical simulation, which was once introduced for the temperature study of DSCCP fiber amplifiers. By experimental measurement and theoretical modeling, it is found that the maximum core temperature is several tens of centimeters away from the injected end of the DSCCP fiber, such that it will distribute the heat load along the longitudinal direction and reduce the maximum thermal load with better thermal management advantages than ordinary double cladding fiber (DCF).

Static and dynamic mode evolution in high-power distributed side-coupled cladding-pumped fiber amplifiers

AbstractWe present a theoretical study of mode evolution in high-power distributed side-coupled cladding-pumped (DSCCP) fiber amplifiers. A semi-analytical model taking the side-pumping schemes, transverse mode competition, and stimulated thermal Rayleigh scattering into consideration has been built, which can model the static and dynamic mode evolution in high-power DSCCP fiber amplifiers. The mode evolution behavior has been investigated with variation of the fiber amplifier parameters, such as the pump power distribution, the length of the DSCCP fiber, the averaged coupling coefficient, the number of the pump cores and the arrangement of the pump cores. Interestingly, it revealed that static mode evolution induced by transverse mode competition is different from the dynamic evolution induced by stimulated thermal Rayleigh scattering. This shows that the high-order mode experiences a slightly higher gain in DSCCP fiber amplifiers, but the mode instability thresholds for DSCCP fiber amplifiers are higher than those for their end-coupled counterparts. By increasing the pump core number and reducing the averaged coupling coefficient, the mode instability threshold can be increased, which indicates that DSCCP fibers can provide additional mitigation strategies of dynamic mode instability.

Study on improving the efficiency of superfluorescent Yb-doped fiber source operating near 980 nm with distributed side-coupled cladding-pumped fiber

Abstract The high-power 980-nm superfluorescent Yb-doped fiber source (SYFS) fabricated with the distributed side-coupled cladding-pumped (DSCCP) fiber is studied with the purpose of improving its efficiency. In experiment, by strengthening the pump light coupling of DSCCP fiber, more-than 23% slope efficiency with the record value of 23-W 980-nm emission is obtained. By means of the numerical study, it is revealed that the 980-nm SYFS efficiency can also be enlarged by optimizing the dopant concentration even with the relatively weak pump coupling, which provides an alternative way to improve the efficiency of SYFS. The pertinent results can be of great importance for studying and designing the 980-nm Yb-doped fiber source.

Experimental investigations on multi-kilowatt all-fiber distributed side-pumped oscillators

3 kW and 4 kW all-fiber distributed side-pumped oscillators, based on a distributed side-coupled cladding-pumped fiber, are demonstrated for the first time, to the best of our knowledge. Using three cascaded gain sections, the 2.95 kW output power with 77.4% slope efficiency and more than 52 dB suppression of stimulated Raman scattering (SRS) is obtained. However, the power scaling is mainly limited by the pump power. By adding one more gain section, the output power is scaled up to 3.96 kW, the slope efficiency is about 73.0% and the SRS suppression is about 48 dB. The transverse mode instability is observed in the 4 kW fiber oscillator, and its dependence on the output power is also measured in experiment.

Generalized study on the pump light propagation in the distributed side-coupled cladding-pumped fiber with identical pump cores

Abstract In this paper, a generalized numerical model describing the pump light propagating in the distributed side-coupled cladding-pumped (DSCCP) fibers with identical pump cores is present, with which the pump light propagation in the DSCCP fiber is analytically investigated. It is found that the local pump absorption should be smaller than the inner-cladding pump absorption of signal fiber. It is also revealed that the DSCCP fiber length for a given total pump absorption should be inversely proportional to the up-limitation of local pump absorption which decreases monotonously with the pump cores number. Furthermore, it is found that the peak pump power coupled into the signal fiber increases monotonously, while its ratio to the total pump power (i.e., normalized peak pump power) decrease monotonously with the increment of pump cores number. The dependences of pump light propagation on the coupling coefficients and the inner-cladding pump absorption of signal fiber are also discussed. We believe that these results can provide significant guidance on understanding and designing of DSCCP fiber and its lasers and amplifiers.

2 kW pump-light-stripper-free distributed side-coupled cladding-pumped fiber oscillator

A 2 kW pump-light-stripper-free all-fiber distributed-pumping oscillator fabricated with the distributed side-coupled cladding-pumped Yb-doped fiber is demonstrated for the first time, to the best of our knowledge. An output power of 1969 W with a slope efficiency of 72.2% is obtained. By utilizing the final-section counter-pumping scheme, pure output spectra free from residual pump light are obtained without using any pump light stripper, which demonstrates that the pump light stripper is not indispensable for this configuration. Besides, no stimulated Raman scattering component is observed in the output spectra. The laser has the M2 factor ranging from 2.0 to 2.6. We believe that the pertinent results are helpful and valuable for designing high-power fiber laser systems.

High-power all-fiberized superfluorescent source with distributed side-coupled cladding-pumped fiber.

An all-fiberized broadband superfluorescent source based on a distributed side-coupled cladding-pumped Yb-doped fiber is demonstrated. A recorded 102W combined output power is obtained with the angle-cleaved output ends. The bandwidth is larger than 10nm. The power scalability of the superfluorescent source is analyzed numerically. It is found that, besides the optical feedback, the active fiber length is another key. The result shows that, by optimizing the active fiber length, it is promising to realize a 600W superfluorescent source with this scheme.

Comparison of fiber lasers based on distributed side-coupled cladding-pumped fibers and double-cladding fibers.

We compare both analytically and numerically the distributed side-coupled cladding-pumped (DSCCP) fiber lasers and double cladding fiber (DCF) lasers. We show that, through optimization of the coupling and absorbing coefficients, the optical-to-optical efficiency of DSCCP fiber lasers can be made as high as that of DCF lasers. At the same time, DSCCP fiber lasers are better than the DCF lasers in terms of thermal management.

分布式侧面耦合包层抽运光纤激光器数值模拟

分布式侧面耦合包层抽运光纤激光器数值模拟

The characteristics of pump light in side-coupled cladding-pumped fibers

The propagation and absorption characteristics of pump light in the side-coupled cladding-pumped active fiber were investigated. A model taking both the absorbing and coupling coefficients into account was established. It is revealed that the absorbing effect of the active fiber enhance the pump-light coupling from the passive fiber to the active fiber, while the coupling effect reduce the absorbing process compared to the common double-cladding fiber. The study also considers the effect of the coupling coefficient ratio. It is found that higher effective absorption coefficient requires bigger absorption coefficient and smaller coupling coefficient ratio.